mb/google/brya: Add variants overridetree.cb path and remove unused registers

Add variants overridetree.cb path remove unused registers

BUG=b:174266035
TEST=Build Test

Signed-off-by: Eric Lai <ericr_lai@compal.corp-partner.google.com>
Change-Id: I2940332044aa4c2de6d58f5d0d2a2a7c1b2c3478
Reviewed-on: https://review.coreboot.org/c/coreboot/+/49920
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
diff --git a/src/mainboard/google/brya/Kconfig b/src/mainboard/google/brya/Kconfig
index d210b4d..b691cd1 100644
--- a/src/mainboard/google/brya/Kconfig
+++ b/src/mainboard/google/brya/Kconfig
@@ -32,6 +32,10 @@
 	string
 	default "variants/baseboard/devicetree.cb"
 
+config OVERRIDE_DEVICETREE
+	string
+	default "variants/\$(CONFIG_VARIANT_DIR)/overridetree.cb"
+
 config MAINBOARD_DIR
 	string
 	default "google/brya"